It is common to chamfer the edge surrounding an opening such as a hole in a workpiece if for no other reason to minimize the possibility of receiving a cut from what might otherwise be a sharp edge or to facilitate insertion of pins and the like into the hole or to provide a mating surface for screws and other fasteners.
There are numerous chamfering tools available that enable one to separately chamfer an edge surrounding a hole in a workpiece. Other tools are available that combine a drilling operation with a single chamfering operation that enables one to chamfer the edge surrounding the hole on the same side from which the hole has been drilled but requires either turning the workpiece over or transporting that tool to the opposite side in order to chamfer the edge surrounding the hole on the opposite side of the workpiece in instances where the hole extends all the way through to the opposite side and a chamfer is desired.
The practice of having to chamfer edges surrounding a hole on opposite sides of a workpiece separately is time consuming and costly and can be extremely so for repetitive operations with large number of units involved even when separate chamfering tools are employed on both sides of the workpiece.